I'm sure that a proper alarm would be a more cost effective and indeed more efficient solution than many of these so called guard dogs. My concern is the growing use of big breeds, like rotweillers, alsations and mastiffs/pit bull, they can and do often get out and then they are a danger!! In many cases the use of the guard dog is cruel as they are chained up, usually to a short chain, all day, so no wonder they get aggresive . I don't blame the dog though, it is the stupid owners who deserve to be chained up!
And don't get me started on the dog howl chorus.......